The two-dimensional electron liquid that forms at the interface between the two insulating non-magnetic oxides LaAlO3 (“LAO”) and SrTiO3 (“STO”) has drawn widespread attention due to its possession of a remarkable variety of emergent behavior including superconductivity, strong Rashba-like spin-orbit coupling, and ferromagnetism. See Ohtomo, A. & Hwang, H. Y., “A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface,” Nature, 427: 423-426 (2004); Reyren et al., “Superconducting interfaces between insulating oxides.” Science, 317: 1196-1199 (2007); Ben Shalom et al., “Tuning Spin-Orbit Coupling and Superconductivity at the SrTiO3/LaAlO3 Interface: A Magnetotransport Study,” Phys. Rev. Lett., 104 (2010); Brinkman, A. et al., “Magnetic effects at the interface between non-magnetic oxides.” Nature Materials, 6: 493-496 (2007).
Despite this interest, the existence and nature of magnetism in structures comprising a LAO/STO interface has remained controversial. Neutron reflectometry measurements by Fitzsimmons et al. on LAO/STO superlattices found no magnetic signatures; their measurements established a bulk upper limit thirty times lower than what was reported by Li et al. See Fitzsimmons et al., “Upper Limit to Magnetism in LaAlO3/SrTiO3 Heterostructures,” Phys. Rev. Lett., 107: 217201 (2011). Salman et al. reported relatively small moments from LAO/STO superlattices (˜2×10−3 μB/unit cell) using β-detected nuclear magnetic resonance. See Salman et al., “Nature of Weak Magnetism in SrTiO3/LaAlO3 Multilayers,” Phys. Rev. Lett., 109: 257207 (2012). As a result, control of such magnetism has remained elusive.